I know you're trying very hard, and I commend you but the fact is, it's doubtful the fascade you've built for your kids and her kids, for that matter, is successful. Kids see and hear everything...and they talk amongst themselves...even if you HAVE been successful, it doesn't mean your SIL has been as well, no matter how hard she may be trying.

Not knowing what the argument was about, makes it difficult to give pertinent advise...depending on kids ages, and the argument, I might suggest talking to them about it, so they understand that while the animosty exists between your H and his sister, they are secure that both sides love THEM unconditionally. Again, not knowing the cause or ages, that's a difficult thing to entertain.

It sounds like you are terribly stressed, and I know I would be under the circumstances. I don't think it's fair how he puts you in this situation, nor how he makes you feel but the role of the peacemaker is never easy. I do understand how he would feel you should 'take his side' but (again not knowing the cause) you may have had very good reasons not to. If he grudgingly understands that...as you've obviously not relented and 'took his side'...then he needs to be advised that his treatment of you and your kids during the visits by his sister, is unexceptable.

Is there a way he can vacate the house while they're there...until they leave, so he can have his temper tantrum without disturbing the household?

I know you said he has a T...perhaps you could go to an appointment with him and ask if there is a way to make him more comfortable with the situation??

Failing that, the fact is, you are a very strong women who is standing by the principles you've layed down for the welfare and well being of your kids and their cousins. Unfortuantely, to continue to maintain this....you're going to have to be just as resolute with your H about his attitude. Obviously, trying to straddle the fence for his benefit is NOT working and is shredding your nerves.

Your decision is therefore: totally appease him and tell your SIL the visits can't go on, or commit to your earlier decision and tell you H to suck it up, or take a vacation when they come. In any case, you, as the peacemaker, deserve a little peace while doing what you can to keep the family together.

I wish you luck and good health...